Balance Sheet Components Regulatory Assets and Liabilities (Details) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014
Current Regulatory Assets [Member]
Regulatory Assets and Liabilities [Line Items]
Price risk management	$ 108	$ 100
Pension and other postretirement plans	0	0
Deferred income taxes	0	0
Debt issuance costs	0	0
Deferred capital projects	5	19
Other	9	14
Total regulatory assets	122	133
Noncurrent Regulatory Assets [Member]
Regulatory Assets and Liabilities [Line Items]
Price risk management	184	121
Pension and other postretirement plans	232	247
Deferred income taxes	87	86
Debt issuance costs	17	15
Deferred capital projects	0	0
Other	27	25
Total regulatory assets	547	494
Current Regulatory Liabilities [Member]
Regulatory Assets and Liabilities [Line Items]
Asset retirement removal costs	0	0
Trojan decommissioning activities	19	23
Asset retirement obligations	0	0
Other	26	37
Total regulatory liabilities	45	60
Noncurrent Regulatory Liabilities [Member]
Regulatory Assets and Liabilities [Line Items]
Asset retirement removal costs	833	804
Trojan decommissioning activities	21	34
Asset retirement obligations	44	39
Other	41	29
Total regulatory liabilities	$ 939	$ 906